Television and telephotographic system



Oct. 19, 1943. E. RElsz 2,332,469

TELEVISION AND TELEPHOTOGRAPHIG SYSTEM Filed June 27, 1941 2 Sheets-Sheet 1 EUGEN REI SZ- INVENTOR Oct. .19, 1943. E. REISZ TELEVISION AND TELEPHOTOGRAPHIC SYSTEM Filed June 27, 1941 2- Sheets-Sheet .2

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Patented Oct. 19, 1943 2,332,469 TELEVISION ANISJYTELEPHOTOGRAPHIC STEM Eugen Reisz, New York, N. Y.

Application June 27, 1941, Serial No. 399,992

can thus neither be used nor canit be adapted 8 Claims.

, This invention relates to television, telephotographic or telecinematographic systems in which reproduction of a picture is obtained by means of a local source of light whose beams are controlled by a number of mechanical oscillators equal to the number of picture elements simultaneously reproduced, said oscillators being tuned to a definite natural or resonance frequency and influenced electromagnetically by currents of low frequency transmitted through a single channel as a combined multi-frequency current and produced and/or controlled by means of light beams, emanating from or reflected by the scene or picture, which are impinging upon photosensitive elements in the transmitter station.

Systems of this type have obviously many advantages. They permit a radical simplification of the structure to be employed and they are not boundto ultra short waves, which exclude long distance transmissions. However the suggestions' thus far made to apply them to television have been unable to show how the requirements necessary toobtain television pictures of a certain minimum'standard can be fulfilled.

It has been proposed, for instance, to reproduce the light conditions of all the picture points of the scene or picture simultaneously by means of spring oscillators, each of which corresponds to one picture element and to use oscillators in the transmitteras well as in the receiver. In former, by causing rhythmical interruptions the light beams impinging upon the photoelectric elements, they produce currents of 9. definite frequency acting as carrier waves for the impulses caused by the light conditions of the picture elements. To keep the oscillatorsof the transmitter operating, energizing impulses conoperated by currents of the proper frequency,

1 when transmitted and they control the light .beams of the local source in conformity with the impulses Ldueto the picture elements.

This arrangement, however, does not allow to use. a number of picture elements even approximately catching up with the minimum necesfor the described purpose.

According to another suggestion made the number of picture elements to be reproduced simultaneously and with it the number of oscillators in the receiver, tuned to a definite frequency is reduced by using a scanning device moved across the image of the scene or picture in the transmitter which scans a linear portion of the same. mitted simultaneously is thus reduced to that of the picture elements of the said linear portion. Identification currents operating the oscillators are necessary and are generated separately by electrical means. They are then modulated by the impulses due to the light conditions of the picture elements. Separate arrangements for each picture element are however nec-' essary in this case.

To control the light beams of the local source in the receiver the oscillators have to operate links actuating shutters through which the light passes. A suitable line shifting device synchronized with the scanning device has to be employed in the receiver.

This arrangement has the obvious drawback of having to provide a separate light impulse converting and identification wave generating arrangement for each picture element, and of having'an insuflicient frame velocity. Its main disadvantage is, however, that even the relatively small number of oscillators for one line (about 150) is not available within the frequency range that can be selected, when the necessary difference between resonance frequencies to avoid failure of operation is maintained and approximately normal scanning and frame velocities are employed.

The present invention has for its object to improve the above described system in such a way that the advantages over the systems now used are;retained while the means for energizing the oscillators, those for producing identifiucation impulses and other features are so selected that the number of picture elements which are 'simultaneously transmitted and that of tuned sary for television or for telecinematographic purposes (equal to about 20,000) nor can it be operated with the required frame velocity. It

oscillators with the necessary security margin attains or surpasses the minimum requirements for television purposes.

" According to this invention the scanning device moving along and scanning a plurality of lines simultaneously is provided with line identification impulse generators consisting of oscil- The number of impulses transoscillators is tuned to a natural frequency differing for a sufficient amount from that of other oscillators and is permanently excited by a suitable frequency generator. The currents operating the oscillators of the receiver are thus not directly produced by an electric generator but are generated by means of the oscillators of the line identification arrangement of the transmitter acting on the light beams which in their turn are converted into electric impulses. On account of the mechanical means employed tuning to a definite frequency attains the highest possible definition.

The permanent energizatlon of the oscillators and the absence of a free oscillation period still further contributes to this result and permits to increase the scanning and the frame shifting velocity to the desired value.

The improvement obtained thus results in reducing to a minimum the diiference between the resonance frequencies of the oscillators, that has to be maintained to exclude operation of a plurality of oscillators with one and the same frequency. Thereby the number of oscillators, and consequently of picture elements, that can be introduced within the narrow frequency band that is accessible and will answer the requirements of television and those of the operating conditions of the oscillators can be increased to a maximum thus attaining or surpassing the minimum number of picture elements in one line that is consistent with the requirements for television and telecinematographic purposes.

Fig. 1 illustrates diagrammatically the principle used according to this invention.

Fig. 2 shows a section through a perspective view of an oscillator arrangement on an enlarged scale.

Fig. 3 shows part of a top view of the same arrangement.

Figs. 4 and 5 show diagrammatically two methods of light control used in connection with this invention.

Fig. 8 shows a detail on an enlarged scale of the modification used in connection with the method shown in Fig. 5.

Fig. 7 illustrates in perspective view part of the oscillator arrangement used in connection with the same method.

Fig. 8 shows an arrangement with a movable carrier for the light control arrangements.

The television or telephotographic system according to this invention and the method of operating it is best described with reference to the diagram shown in Fig. l, which represents the main parts of the system, without regard to size or to the number of parts used. To avoid crowding of the figures, outlining the method used, a light control and oscillator arrangement with a straight path of the light rays is indicated, but it is to be understood that the oscillators and the light control method illustrated in detail in Figs. 2 to 'l are to be employed. A transmitter T and a receiver R. operatively connected by a wireless transmitting and receiving arrangement 25 and 26 respectively are shown in the diagram. The scene or object I (represented by a cross) contained within an area 5 or the projection of a picture on a screen 5' (shown in dotted lines) is resolved into elemental areas 8 the light values of which have to be reproduced separately. For this purpose a scanning device is arranged, which is capable of scanning a linear portion of the picture. Such linear portions which are scanned successively are indicated by transverse lines ab, 0-11, 0-!

. line a-b being shown as subdivided into the required number of elemental areas, the small number represented in the diagram being not representative of the number of elemental areas used in practice which if possible is above or closely approximates 150.

The scene or picture is lighted by a source of light 2 arranged either in front or behind the scene or the screen and the light emitted by the source of light or reflected by the objects l'oi the scene or by the picture passes through a lens system 3 and through the scanning device I on to a photoelectric cell 4 or to a plurality of such cells.

The scanning arrangement I is located in the focal plane of the lens system 3 and its construction and operation will be explained later in detail. For the purpose of describing the system it is suflicient to mention that merely the light beams of a transverse line of the scene or picsuch a means may consist in an arrangement for moving the arrangement I across the picture. It is however preferable to move the rays of light only by means of a mirror wheel or an oscillating mirror.

During this scanning movement either of the arrangement itself or of a ray directing means each individual device I, 11" will be traversed by light beams from one longitudinal line of the picture only. Each device is therefore permanently associated with one of the longitudinal lines. For identification purposes said devices I 1" are provided with oscillators, such as springs 8 which are of such dimensions and are so arranged that they will oscillate with 8. definite natural frequency when excited. The resonance frequency of each spring differs from that of every other spring in the series and it is therefore used as an identifying factor, permitting to identify the longitudinal line, whose light beams are passing through the device.

When oscillating each device is capable of intercepting deflecting or otherwise influencing the light' beam during its passage in such a. way that its action on the photoelectric cell is rhythmically intermittent. The impulsesdue to the scanning of a longitudinal line are therefore superposed and are modulating the line identification impulses produced by the oscillation of the springs 8.

Beneath the oscillators 8, which are made of magnetic material an electromagnet 9 is arranged in a circuit III which contains a frequency generator permanently producing all the frequencies that are used in connection with the light control arrangement. These frequencies may be superposed on a D. C.

After having passed the scanning arrangement 1 the beams impinge upon the photoelectric cell 4 where they produce electric impulses. The circuit 20 which contains the photoelectric cell or cells will therefore carry all the frequencies that have been produced by the action'of the oscillators devices on the beams of light passing I ing to the frequencies through them. This circuit moreover, besides containing a source of high tension, will include an amplifier for the frequencies generated in the type and construction as that already mentioned,

springs l8, an electromagnet l9 foroperating the springs and a circuit 21 connected with the demodulator of the radio receiver 28. The individual control devices for the light beams are giving passage to or deflecting the beams of light in such a way that they reach a screen or an observer behind the control devices whenever they are actuated rhythmically by one of the spring oscillators. Every oscillator of the series I8 is tuned to a natural frequency differing from that of every other oscillator, but is identical with one of the resonance frequencies generated in the transmitter. Oscillators belonging to corresponding longitudinal lines have the same natural frequency.

Behind the light control arrangement I! the observer may directly be placed as indicated on the drawings by the eye 30. In other arrangements and where it is to be preferred to view a projected picture a screen 32 shown partly in dotted lines may be used.

To reproduce the entire picture or scene a movement of the light rays by means of an oscillating mirror or a movement of the light control arrangement l'l, brings successively, reproduced lines in their proper positions with respect to each other. The latter case is indicated in the figure by the arrows, though the former is the case actually preferred.

The operation of the arrangement described is the following.

Assuming that transverse line a,b faces the scanning arrangement 1 at a given moment, then the light emanating from or reflected by the small elemental areas of this line will pass through the devices I, 1". The circuit ill of the electromagnet 9 is permanently fed by a pulsating current containing all the frequencies allotted to the springs or oscillators 8; therefore all the oscillators will vibrate with their resonance frequency. A light beam passing through one of the devices will thus be rhythmically interrupted, intercepted or deflected and will reach the photoelectric cell or cells 4 only intermittently. the

, rhythm of the interruptions or deflections reproducing the frequency with which the spring 8 is oscillating.

Line a-b contain lighted areas .tothe left and to the right and dark areas in the central portion. No light beams will therefore be emitted by the central elemental areas and pass through the central light control devices 1'. The pulsating current in the circuit v2i) therefore contains the pulsations or oscillations correspondruption of the light beams at the right and at the left. The frequencies of the springs actuating the light control devices 'l" in the central due to the rhythmic interpart are therefore missing as no light beam passed through them to the photoelectric cells.

Currents with all the frequencies that are present are now passed on to the radio transmitter 25. and are used for modulating the carrier wave.

In the receiving station R the pulsating low frequency currents, after having been picked up and demodulated by the radio receiver 26 enter circuit 21 containing the electromagnet i9. As frequenciesof springs operating devices at the right and at the left are present, the corresponding springs will oscillate in the receiver and will open and close rhythmically the light control devices associated with them. The frequencies corresponding to the (three) central springs are missing in the transmitter and are therefore absent in the receiver. The light control device I'I in the center are not operated as the springs do not find a frequency with which they are in resonance. A line conslstingof light spots at the right and at'the left will be viewed by the observer 3!! or appear on the screen along the line a'b'. This line will be a replica of the line a- -b. i When the scanning arrangement meanwhile continues its movement, each device 1', 'I" will be traversed by the light beams proceeding from successively scanned elemental areas of a longitudinal line. Impulses due to the varying light conditions along the line will act on the photoelectric cell 4. For instance, when line c-d will be in operative position all the light rays are interceptedby the horizontal beam of the cross and all the frequencies are eliminated from the current flowing to the radio transmitter 25. Dark areas alone will therefore be viewed along the line c'-d' in the receiver.

When the scanning device proceeds towards line g-n, the devices I and 'I" on the right and on the left will again give passage to beams passing through them. The beams proceeding from each longitudinal line pass through the same device I, 'I" and therefore the impulses from that line will b associated with the frequency corresponding to that of the springs 8 of the respective device. The central devices 'I' will not receive light rays and their frequencies will therefore not appear in the pulsating currents. The result will be the same as that described already with respect to line a-b. A dark portion of the width of the vertical beam of the cross will be seen on line ef', the other portions being lighted.

Assuming now that the beams of the cross are not completely dark but that they reflect some light so that half tones are present. When considering the operation under these conditions, with line a-b facing the scanning arrangement, it is clear that beams passing through the central devices 1", though of less intensity than those passing to the right and to the left, will reach the photoelectric cell 4 and will cause a pulsation in the current corresponding to the frequency of its oscillator springs. In the receiver the devices l1""inthe central part of the line will therefore be operated. The amplitude of the current oscillation set up within the photoelectric cell is however smaller'than that of currents produced by light beams of greater intensity as the half lighted areas are influencing the photosensitive elements to a less extent. Currents of the same frequency but of less amplitude are therefore produced. The reduced amplitude of the currents in the transmitter causes a reduced amplitude of the oscillation of the' oscillator springs I8 and thereby an operation of th light control device reducing the volume of light admitted to Passage. The observer in the receiving station will thus perceive a spot of light of less intensity. The half tones or half lights are thus exactly reproduced.

It will thus be seen that during the scanning operation a number of impulses of varying intensity clue to the advance of the scanning device is produced by means of the beams passing through one of the devices. These impulses of varying intensity are superposed on those produced by the springs which are rhythmical and more rapid. The impulses due to the scanning of a longitudinal line are thus associated by way of modulation, with those produced by the line identification means, which serve to guide-them to the proper spring with the identical resonance frequency in the receiver. In this way the light control devices in the receiver are associated with the longitudinal lines in the scene or' picture and are able to reproduce the impulses due to the scanning of the line, especially if the rhythmical influence is so chosen that it cannot be perceived.

The light control arrangement to be employed in television or telephotographic systems of the type described is shown in several modifications in Figs. 2, 3, 4 to 9. It consists of several parts illustrated separately. An essential part of the light control arrangement consists of the spring oscillators 8, l8 (Fig. 1) BI, 82 (Figs. 2-9) which are so dimensioned and seated and held in such a. way that each of them has a definite natural frequency of oscillation. Either round or square or rectangular profiles may be used for the springs. A distribution of the load. including that due to the weight, which excludes an increase of the load towards the free end is of advantage and secures a sharply defined resonance.

As shown in Figs. 2 and 3 the arrangement consists of an electromagnet with a core 39 finely subdivided and lamellated in the direction shown in the drawings. This core carries a winding 4l. A permanent magnet 43 holds said core and winding and also supports the carrier or bank 42 for the springs 8|. 8!, 83 Said carrier may be fastened to the permanent magnet r b any appropriate means or may simply be slid over the head of the magnet.

On the s ring bank or spring carrier 42 the springs 8|, 82 are fastened in any appropriate fashion. In Fig. 2 they are shown as held in indentations between teeth of the bank or carrier 42. The latter is comparatively heavy to resist any tendency to oscillate with the springs.

As explained the resonance frequency of the sprin s differs and this difference may be obtained by arranging the springs in such a. way that different lengths of the springs protrude freely from the bank or carrier 42. It is however preferable to cut all the springs to the same length and to mount them on the spring bank or carrier 42 in the same way. To vary the free length of thesprings a separate spring support member 44 is used which may be integral with the carrier 42 but preferably forms a separate unit that can be easily interchanged. Said support member 44 carries a tooth projection or knife edge 45 firmly pressed against the spring when the support member is in its position on the bank or carrier. The point of contact of the tooth or knife edge 45 with the spring oscillator will determine the free length of the spring with which it will oscillate.

The series of teeth or knife edges for the various spring oscillators may form a curve (Fig. 3) so that the free length of the springs varies in some regular manner from spring to spring. This curve can be arbitrarily chosen. The knife edges along the support member may however also vary in some irregular way.

It may be of advantage to use a plurality of support members with teeth or knife edges running along different curves, which can be easily exchanged. This method may especially be useful for transmissions of pictures or scenes that are to be kept secret. As will be clear from the description given above oscillators with the same natural frequency must be located on the spring banks at corresponding places in the transmitter and in the receiver. Otherwise no reproduction is possible. An irregular distribution of the frequencies or an everchanging distribution of the frequencies by means of interchangeable support members will therefore constitute a, complete bar against unwanted reception and reproduction.

It is to be noted that springs are necessary for this particular purpose of controlling and operating light control devices in the transmitter. Springs are susceptible of being tuned to resonance with a precision which is not obtainable with electrical means within the frequency range which has to be used in this case. The number of springs that can be accommodated within 'a given frequency range is therefore increased, an advantage which is of the greatest importance, on account of the restricted range that is suitable for television purposes. The most suitable range covers only frequencies between 5000 and 10,000. Springs operating reliably with a resonance frequency of 10,000 and above cannot be found.

With frequencies below 5000 the performance has a tendency to become poorer and poorer on account of the necessary decrease of the scanning and frame shifting velocity, entailed by the increase of the length of the period for starting and for the fading of the resonance oscillation with lower frequencies.

Moreover the number of sufficiently differentiated frequencies to which oscillators may be tuned decreases rapidly when the frequency decreases. The difference between the natural frequencies of oscillation of two springs may be greater but it should always be kept relatively small, as it in important that every sprin i kept in a state of readiness to go into resonance within the shortest possible time. It has been found by practical experience that the period of time elapsing between the appearance of the resonance frequency in the electromagnet and the actual appearance of a state of resonance in the spring is much longer when the spring is at rest and is appreciably shortened when the spring is in a state of beginning resonance on the lower part of the resonance line. When resonance frequencies are employed differing from each other only slightly such a state of preliminary oscillation is prevailing in the entire group of springs.

Moreover the selection of frequencies which ar only slightly different is necessary to accommodate the required number of springs and of control devices within a given interval.

Selection of a suitable spring material, and of a suitable method to hold or grip the springs and a small damping factor in air will moreover contribute to the springs readiness to reach very rapidly the apex of the resonance line.

The masses that have to be moved have to be kept very small and have to be distributed in such a way that their influence is negligible so that they will not materially affect the period of I time during which resonance is developing.

The methods used to control light beams direct: 1y or indirectly by means of oscillating springs are shown in Figs. 4 to 9, Figs. 4 and 5 showing two methods of controlling light beams by the oscillator springs themselves, while Figs. 6 and '1 show details of the arrangement.

According to Figs. 4, 6 and '7, illustrating diagrammatically on a greatly enlarged scale an arrangement used in a receiver, the end faces 88 of the oscillator springs 8|, 82 which are formed by wires with a circular cross section, are

- either polished or varnished or otherwise flnished so as to reflect light in a diffused condition. Immediately in front of said end faces 88 a rib-. bon, a flat metal band, a wire or the like 88 is stretched along the entire bank of springs. The

\ width of the band may eitheebe equal to the diameter of the springs or may be-somewhat in excess of said diameter. It forms a screen behind which the polished end faces of the oscillator springs are located in their position of rest spring 8| will leave its place behind the band screen 86 and will periodically appear and disappear behind the band screen. When uncovered by the band screen the polished end face of the spring will reflect the light beams from the source of light 28 towards the mirror. Thus areas under different. light conditions will be seen along the edges of the band screen when viewed from the central part of mirror-41, which are exactly reproducing light conditions in corresponding areas of the scene scanned at the same time in the transmitter (Fig.6).

The minimum length of the springs is preferably so chosen that the greatest amplitude of the oscillation will just be suflicient to uncover the entire end face or a substantial part of it. A smaller amplitude of the current oscillating the spring-corresponding to a light beam of less intensity and to a smaller volume of light passing or are screened when they are in a state of preliminary oscillation, as above described. The band may be blackened or may receive a superflcial treatment so as to reflect no light rays.

Behind the band screen 88 and in front of the end faces 88 a local source of light is arranged. To utilize its light to the fullest extent so as to obtain brilliantly lit views or pictures various means may be arranged. A very simple and effective method consists in using a source of light 28 with a long drawn incandescent filament, approximately of the same length as the spring bank and to arrange it as closely as possible to the end faces'of the springs.

A mirror 41 arranged at some distance in front of the end faces 88 receives light beams reflected from the end faces. The mirror is oscillated with a definite frequency, related to the frame velocity. The oscillation may be produced by an electromagnet energized by a current of the required frequency, which may be one of the beat frequencies produced by the interference of two frequencies used in the arrangement.

This arrangement reproduces the light conditions in a group of elemental areas in accordance with the passage of light beams from these areas through the light control devices of a. transmitter. Assuming in accordance with Fig. 1 that the receiver represented in Fig. 7 is operated by a transmitter possessing an identical set of springs and that springs responsive to the same frequency are located at identical places within the set, the operation is the following.

A beam of light passing through a light control device in the transmitter operated by a spring corresponding to spring 8| in the receiver will set up oscillations of a frequency which is in resonance with the natural frequency of spring 8| in the manner described with reference to Fig. 1. The intensity of the light beam passing through said light control device will determine the amplitude of the current actuating the spring.

- This current, when transmitted to the receiver will cause spring 8| to oscillate, as it is in resonance with this frequency (provided any light at all passed through the device in the transmitter) and therefore the polished through the control device within the given period, during which the group is scanned-will cause an oscillation of the spring 8| with a reduced amplitude whereby the area of the end face 88 appearing behind the band screen and active as a reflecting device for the light beams from the sourceof light 28 is reduced. The volume of light sent to the mirror 41 is reduced accordingly. The elemental area in this case when viewed from the mirror is half lighted only on account of the reduced volume of light sent to it by the spring and therefore half tones are reproduced exactly on account of the proportionality between the amplitude of the current received and the amplitude of the oscillating spring.

The lighted, half lighted and dark areas appearing along both edges of the band screen form a. line or group that will appear in'the central part of the mirror 41 and by virtue of the oscillations of the mirror successive images of these groups or lines will appear in juxtaposition to the observer 30. As the oscillation of the mirror 41 is synchronized with the oscillation of a corresponding mirror or the movement of another scanning device'in the transmitter successively scanned transverse lines are thus appearing in the exact relative position they occupy on the scene or picture.

Fig. 5 illustrates diagrammatically another method of controlling the light rays by deflection, using the end faces of the springs as deflecting agencies. a s

The figure shows thegreatly enlarged end of an oscillator spring 8| of circular cross section which is provided with two flat and highly polished surfaces 8| and 82 arranged at an angle to each other so that an edge will result between them. The angle of inclination towards a plane perpendicular to the axis of the spring is very small and the angle or shown in the diagram has been enlarged to obtain a better representation.

The arrangement shown in Fig. 5 is that used in a receiver. It comprises a source of light 28,

preferably of the type described in connection end face 88 of the of a line will appear on the screen when the light beams are deflected in this direction. Behind the screen an oscillating mirror 98 is arranged, whic has the form of a narrow strip and which oscillates at a frequency proportional to the line scanning and frame velocity. The observer may look directly into the mirror or he may look towards a screen 32 on which the picture is thrown by the mirror.

When the springs are at rest the screen 86 is not lighted as the light from the local source of light 28 will fall mainly on the edge between the two polished faces. Whatever light may reach the faces 9!, 82 of the springs is not deflected towards the screen 96. As soon as a spring begins to oscillate the light beams from the source of light are deflected and are sweeping over the diaphragm and the screen 96. Each spring, during its oscillation, therefore periodically lights an elemental area of the strip or line appearing on the screen. The distance and the angles are so chosen that the slot 91 in the diaphragm is fully lit when the springis oscillating with its greatest amplitude, while the deflected beam is partly intercepted by the diaphragm 86' when the oscillation of the spring does not reach the maximum value.

The mirror 98 reflects the image of the line produced on the screen towards the observer 30 and as already stated will placesuccessively appearing lines into their proper space relation and spread them over the area of the scene or picture.

The arrangements shown in Figs. 4 to '7 may be used in the transmitter as well as in the receiver with the modification that the scene or picture takes the place of the observer 30, while the photoelectric cell takes the place assigned to the local source of light 28. The light beams change their direction but otherwise the construction and operation is the same. In Fig. 5 there is a further change in that the'slotted diaphragm may be dispensed with. Moreover screen 96 may in many cases be omitted in the transmitter.

The mirror illustrated in Figs. 4 and 5 respectively is a narrow strip of glass or metal oscillated by an electromagnet 48. The latter may be energized by one of the beat frequencies which can be obtained from the various frequencies used in this arrangement. Alternatively the mirror may be driven by a motor. The movement of the mirror in the receiver must be synchronous with that of the scanning mirror in the transmitter.

The speed with which the mirror oscillates is relatively low. It depends on the line scanning speed and on the frame velocity. It will increase with the number of lines and with the frame velocity.

In Fig. 8 another method of scanning the groups of elemental areas is shown diagrammatically. The scene or picture I indicated as in Fig. 1 by means of a cross contained within an area 5 is scanned by the light control arrangement 1 which is a self contained unit and is rotated for this purpose. In the transmitter the photoelectric cells may be mounted behind the arrangement 1 and may rotate with it.

The light control arrangement 1 may be mounted on a disk 49 of a diameter which is larger than one of the dimensions of the picture or scene area 5 so that said area covers a sector only and the light control arrangement passes over the area during a part of its rotation. The lines scanned simultaneously are no longer straight lines and the elemental areas acting simultaneously on the photoelectric cells are no longer arranged in transverse lines but on lines inclined to each other to a varying degree.

The lines scanned in this case are curved lines sive groups ab, c-d intersecting the lines at varying angles as indicated in dotted lines on the figure.

Instead of one disc carrying a plurality of light control arrangements, two rotating arrangements or groups of arrangements with centers of rotation at opposite sides of the area of the scene or picture may be employed. Such an arrangement eliminates irregularities due to the uneven distribution of the groups over the area and reduces the speed of rotation as higher frame velocities are obtained by such an arrangement.

By introducing mechanical oscillators between the electric frequency generator, providing the line identification impulses, and the transmission channel leading to the receiver the sharp definition of the resonance frequency arriving at the receiving end is greatly increased. It is thus possible to use oscillators tuned to resonance frequencies with a minimum difference between said frequencies. The smallest possible difference is necessary to obtain the requisite number of oscillators, while remaining within the narrow frequency range which is available for this purpose. Only in this way can the minimum number of picture elements, each represented by an oscillator, for a line in a television or telecinematographic arrangement be obtained.

The system and the method have the further great advantage that a mechanical transmission can be used by means of recording in the well known fashion. The combined oscillation'which is to be transmitted may be recorded on a disc or drum in the manner in use for sound recording and the receiver may be actuated by oscillations that have been generated mechanically by means of a needle operated by the record.

What I claim is:

1. In a television or telecinematographic system a transmitter comprising a photo-sensitive element and an operative circuit therefor, a scanning device for simultaneously scanning a plurality of lines, line identification impulse generators, some elements of which are inserted between each line and the photo-sensitive element, and which comprise spring oscillators tuned to a definite resonance frequency, differing from that of other oscillators, rhythmically interrupting the passage of light toward the photo-sensitive element, the said lineidentiflcation impulse generators thus producing in the circuit of the cies, identical with those to which the oscillators of the line identification impulse generator are tuned and operated by the currents generated by the same and a line shifting deicrlice operated in synchronism with the scanning evice.

2. In a television or telecinematographic system a transmitter comprising a photoelectric element and an operative circuit therefor, a scanning device scanning simultaneously a plurality of lines, line identification impulse generators, comprising mechanical oscillators, each tuned to a definite frequency differing from that to which the other oscillators are tuned, electromagnetic means for energizing said oscillators, an operative circuit for said means and a frequency generator, connected with said circuit,

producing permanently a multifrequency current with component frequencies equal to the resonance frequencies of the oscillators, so as to energize permanently and simultaneously all the oscillators of the impulse generator, said oscillators being positioned in the path of the light rays proceeding from the scene or picture towards the photosensitive element and controlling the passage of light thereto, the said line identification impulse generators producing in the circuit of the photosensitive cell a multifrequency current in which each component has a definite frequency modulated by the impulses of a single longitudinal line, and means to transmit said multifrequency current to the transmission channel.

3. In a television system according to claim 2 spring oscillators with a substantially uniform distribution of the vibrating masses along the free length of the vibrating parts and with operative end faces.

4. In a television system according to claim 2 a group of spring oscillators arranged in a series,

a carrier for said group provided with means for gripping the fixed ends of the oscillators means for fixing the free length of the springs independently of the fixation of the ends, associated with the carrier and comprising a supporting member firmly pressed against the spring which determines the length of the spring which is free to oscillate.

5. In a television system according to claim 2 a group of spring oscillators arranged in a series, a carrier for said group provided with means for oscillator spring individually and differently from that of other oscillator springs comprising an interchangeable pressure member with parts pressed against each spring, when attached to 'the carrier, the foremost point of, the part pressed against each spring determining its free length, capable of vibration, a number of different pressure members being adapted to be attached and to cooperate withthe carrier, the different members having those parts which. are pressed against the springs arranged differently, so that the free length of the same oscillator spring varies when different pressure members are attached to the carrier.

6. In a television system according to claim 2 a series of spring oscillators arranged side by side, each oscillator being of substantially uniform cross section, the faces at the end of the oscillators being arranged substantially in a line and adapted to reflectlight falling on them, an opaque screening strip covering these faces when the oscillators are at rest, the faces of said oscillators being uncovered and brought into a position in which they reflect light falling on them, the volume of the light reflected being dependent on the amplitude of the oscillator. i

'7. In a television system according to claim 2 a receiver comprising a local source of light, a series of oscillators of substantially uniform cross section, provided with reflecting end faces substantially of the same area as the cross sections and adapted to reflect light diffusely.

8. In a television system according to claim 2 a series of spring oscillators of substantially uniform cross section arranged side by side, with their end faces arranged substantially in a line and all end faces having substantially the same cross section and being adapted to reflect light falling on them, an opaque screening strip, somewhat wider than the dimensions of the end faces in the direction of oscillation, covering said end faces, when the oscillators are not oscillating with their resonance frequency while these faces are uncovered when resonance has been reached.

EUGEN REISZ. 

